Right got the car working and MOTd today

Got a problem which ive had for awhile to do with the Idle Speed Control Valve with my Focus inlet setup.

Basically once the car is up to temp the revs sort of stick and the car bogs down a loses power. Its fine when its cold with no sticky revs and loads of power.

Ive been told the revs sticking is down to the Focus ISCV not being compatible with the mondeo management. The solution is to get a ISCV off an Escort which im going to do.

But my question is would this cause a loss in power aswell? What does is ISCV doing differently when the car is up to temp compared to when its cold?